Rugged electric clock movement



July 21, 1964 P. G. GERHARD 3,141,290

EUCCEE ELECTRIC CLOCK MOVEMENT Filed Nov. 1, 1963 Jj. www

,Sais

United States Patent O" 3,141,290 RUGGEE) ELElTRlC CLOCK MOVEMENT Paul G. Gerhard, Washington, 11C., assignor to the United States of America as represented by the Secretary of the Army Filed Nov. 1, 1963, Ser. No. 320,971 3 Claims. (Cl. SS-ZS) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to me of any royalty thereon.

This invention relates to clock mechanisms, and more particularly to a rugged electric clock mechanism having a long shelf life, and which can be used to perform ordnance timing operations.

Clock mechanisms for use in ordnance applications must meet standards and criteria not found or needed in other applications. A high degree of long term accuracy is not necessary, but the mechanism must be rugged, simple, and inexpensive. Additionally, military specilications require that clock mechanisms which are to be used in land mines and other similar ordnance applications operate for periods of time longer than that obtainable from spring driven clocks. To meet the requirements of ruggedness, low cost, and long operation electrically powered timing mechanisms have been proposed for ordnance applications. The diiiculty with such mechanisms is that oxides and films tend to form on the electrical contacts during storage and shipment, making their operation unreliable.

One object of this invention is to provide a reliable electrically powered clock mechanism which has a long shelf life.

In order that the power supply used to drive the electric clock mechanism be reasonable in size and cost, it is necessary that the clock mechanism have a low current drain. Therefore, another object of this invention is to provide an electric clock mechanism having a minimum number of contacting parts, reducing friction and electrical losses to a minimum.

A more specific object of the invention is to provide an electric clock mechanism having self cleaning contacts.

An additional object of this invention is to provide an electric timing mechanism which can provide fail safe operation. That is, in fuzing applications, if the clock fails it is desirable that the fuze be unarmed.

These and other objects of this invention are accomplished by using a tilting index wheel and making the electrical contact identical with the mechanical contact between the indexing wheel and the indexing pin. In this manner, the number of contacting parts is a minimum reducing the drag on the indexing wheel to a minimum, and the sliding action between the indexing pin and the tilting indexing wheel provides a self cleaning action for the electrical contacts.

The specific nature of the invention, as well as other objects, uses and advantages thereof, will clearly appear from the following description and from the accompanying drawings, in which:

FlG. l is a plan view of the timing mechanism of this invention with the left side of the top cutaway.

FlG. 2 is a side elevation of the clock mechanism of this invention showing the index wheel in the drive position.

FlG. 3 is a side elevation, similar to FIG. 2, showing the indexing wheel in the tilted position.

FIG. 4 shows one embodiment of the combination contact-index pin constructed in accordance with the teaching of this invention.

FIG. 5 shows another embodiment of the combination P ICC 2 contact-index pin constructed in accordance with the teachings of this invention.

Referring to FIGS. 1 and 2, a balance wheel 10 is mounted upon a shaft 11 for oscillation. Fixed to the periphery of the balance wheel lil is an indexing pin 12. As is more clearly shown in FlGS. 4 and 5, the upper end of the pin 12 is liush with the upper planar surface of the index wheel 14. Pin 12 is beveled at its upper end to form an incline surface 13. The lowest point of the inclined surface 13 should be slightly below the lower planar surface of the index wheel 14 to insure that the pin slides underneath the wheel. g

Shaft 15 is tapered abruptly at both ends. The shaft 15 contacts the edge of circular hole 19 formed in the housing Ztl so that the upper end of the shaft 15 can move longitudinally in oval slot 22. Hole 19 has a diameter which is large enough to allow pivotal movement of the lower end of the shaft 15 therein. ln order to clearly illustrate the position of shaft 15 in hole 19 and slot 22, the housing 2d has been shown to be composed of clear plastic. Of course, housing 2t) may be composed of any suitable material within the scope of this invention.

Shaft 15 is returned to a vertical position with respect to the housing 2u by permanent magnet 23. Magnet 23 is positioned opposite a magnetizable circular disc 24, which is cemented or otherwise fixed to the lower surface of index wheel 14.

Attached to the shaft 15 is a gear 25 which drives a second gear 26, the latter gear meshing with other gears in a gear train (not shown). Rotation of gear 26 can be utilized to close an electrical switch or any other purpose, as will be apparent to those skilled in the art.

Surrounding the `balance wheel 10 is a C shaped magnetic core 31, which has opposed poles 31a and 311:. A magnetizing coil 33 is wrapped around the core 31, and the coil 33 is energized by a battery 32. A hair spring 34 is attached at one end to shaft 11 and secured at the other end to a post 35, which is affixed to the housing 2t). As is common in the art, the hair spring 34 exerts a restoring force on the balance wheel 10 when it has been rotated by the energized magnetic core 31. One end of the magnetizing coil 33 is connected to post 35 and hair spring 34. lf housing Ztl is made of a conducting material, the post 35 must be insulated from the housing and the shaft 11 should be insulated from the housing by insulating, or jeweled bearings, 36a and 36b. One side of the battery 32 is connected to the coil 33 and the other side of the battery 32 is connected to shaft 15. If housing 2) is made of a nonconducting material, the connection to shaft 15 may be accomplishhed by using a conducting liner in hole 19, as shown.

The electrical circuit for the clock mechanism may be traced, starting at the positive side of the battery 32, through the coil 33, hair spring 34, post 11, balance wheel 10, beveled pin 12, index wheel 14, shaft 15, and back to the negative side of the battery. As will be apparent to those skilled in the art, the circuit is complete when beveled pin 12 makes contact with index wheel 14, and the circuit is broken when the beveled pin and index wheel are out of contact.

In operation the mechanism is an impulse type electric clock, that is, each time the balance wheel 10 makes one oscillation an electrical impulse is applied to coil 33, and armatures 31a and 31h magnetically attract a soft iron armature 10A positioned on the balance wheel 10. Thus, a rotational force is periodically applied to the balance wheel, keeping it oscillating. As the balance Wheel 10 rotates in the direction B, the beveled pin 12 pushes the index wheel 14 ahead one tooth. Rotation of the balance wheel 10 in the opposite direction tilts the index wheel 14 as the sloping surface 13 of pin 12 slides underneath the index wheel tooth. The elongated hole 22 in the top plate allows the shaft to be displaced, while permanent magnet 23 underneath the index wheel returns the wheel to its normal position after the pin 12 has passed beneath a tooth. A pivoted arm 36, which is biased by a permanent magnet 37 drops in back of the index teeth as the wheel is moved ahead, and thus keeps the wheel from rotating in the reverse direction as the pin 12 slides underneath. In the drawing, the pivoted arm 36 is resting on the tip of a tooth since the index wheel is in the process of being pushed ahead.

Since it is not necessary that the pin 12 clear the index wheel 14 on its return, the pin 12 may push each tooth completely ahead so that the succeeding tooth will be in place to be pushed ahead by pin l2, held there by arm 36. In this manner oscillation of the balance wheel 10 can be made impossible when the index wheel 14 is jammed, and this provides a fail-safe feature. By powering the detonator from a supply inductively coupled to the coil 33, a jamming of the timing mechanism prevents the periodic making and breaking of the circuit, which prevents the alternate buildup and collapse of the magnetic l'ield, which in turn would remove the power from the detonator.

FIGS. 4 and 5 show in detail two embodiments of the novel contacting system of this invention, which applies a pulse tothe electro-magnet during each oscillation of the balance wheel. The same components which convert the oscillatory motion of the balance wheel to rotational motion of the index wheel make up the contacting system; no additional components are used. The embodiment of FIG. 4 shows an uninsulated version of the pin 12. As the beveled pin 12, in the embodiment of FIG. 4, strikes a tooth of the index Wheel 14 in the process of pushing the wheel ahead, the electrical circuit between the pin 12 and the wheel 14 is completed and the electro-magnet 3133 is energized. At this time the armature is approaching the pole pieces 31a and Sllb, as shown in FIG. 1, and is pulled toward the pole pieces by the magnetic field. Before the armature has lined up with the pole pieces 31a and 31b, the beveled pin 12 has moved beyond the teeth of the index wheel 14, and the electric circuit is 34 in the opposite direction and the pin 12 tilts the index wheel 14, the electric circuit is again closed. At this time the armature is moving away from the pole pieces, and the magnetic field applies a breaking force; however, by having narrow teeth on the index wheel and a sharp slope on the beveled pin 12, as shown in the embodiment of FIG. 4, the duration of contact is so short as to be negligible. In pushing wheel ahead, a force of several thousand pounds per square inch is developed between the index wheel 14 and the pin 12, and this force insures reliable electrical contact. Additionally, some wiping and cleanembodiment of FIG. 4 the desired electrical contact for the pin slid under the wheel the duration of this contact was so short as to be insignificant. In the embodiment of FIG. 5, the situation is reversed, that is, the desired contact is made as the pin 12 moves under the index wheel rial 38 to the front of the pin in order to prevent electrical contact as the index wheel is pushed ahead. The advan- 4t tage of the embodiment of FIG. 5 is that better cleaning action is provided between the contacts as the pin scrapes under the edge of the index wheel teeth. However, the insulated pin of the embodiment of FIG. 5 is more expensive than the uninsulated pin of FIG. 4.

FIG. 5 operates essentially the same as FIG. 4. As the pin 12 slides under the index wheel 14, the coil 33 is energized attracting the pole pieces 10a on the balance wheel 10. Contact is broken after the pin has passed under the tooth, and the hair spring 34 powers the balance wheel to move in the opposite direction causing the insulated front of pin 12 to push the index wheel ahead.

In operation, the iirst l to 26 oscillators of the balance wheel 10 will be powered mechanically from without the timing mechanism as the fuze is set. This starts the contact cleaning action, and the contacts are thereafter Continually cleaned throughout the operation of the timer.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

I claim as my invention:

1. An electric timing mechanism comprising:

(a) a balance wheel mounted for oscillatory movement, and an index wheel mounted for rotation about an axis perpendicular to the plane of said balance wheel, the plane of said index wheel being parallel to the plane of said balance wheel during rotation of said index wheel,

(b) said index wheel tiltable a predetermined amount in said plane, and a series of teeth spaced around the periphery of said index wheel, said teeth overlapping a portion of the periphery of said balance wheel,

(C) a pin xed adjacent the periphery of said balance wheel with the longitudinal axis thereof perpendicular to said plane, said pin being small enough to enter the space between adjacent index wheel teeth, said pin having a perpendicular surface which engages a tooth of said index wheel upon movement of said balance wheel in one direction, and said pin having an inclined surface tilting said tooth and said index wheel said predetermined amount which is sucient to allow said pin to pass under said tooth and into the space between said tooth and an adjacent index wheel tooth,

(d) an electro-magnet having alined opposed poles, said balance wheel being centrally disposed between said poles, and an armature connected to said balance wheel with its longitudinal axis intercepting the axis of rotation of said wheel,

(e) means to periodically energize said electro-magnet, said means to energize including said pin and said index wheel, said pin and index wheel periodically making and breaking a circuit between said electro-magnet and a power supply whereby the wiping action caused by the relative movement between said pin and said index wheel frees said contacts of corrosion.

2. An electrical timing mechanism as in claim 1 wherein said inclined surface of said pin is sharply sloped and said contact is made when said perpendicular surface of said pin engages said tooth, the duration of Contact between said inclined surface and said index wheel teeth being short.

3. An electric timing device as in claim 1 wherein said perpendicular surface of said pin is insulated, said slope is gradual, and contact is made when said index wheel slides over said pin` No references cited, 

1. AN ELECTRIC TIMING MECHANISM COMPRISING: (A) A BALANCE WHEEL MOUNTED FOR OSCILLATORY MOVEMENT, AND AN INDEX WHEEL MOUNTED FOR ROTATION ABOUT AN AXIS PERPENDICULAR TO THE PLANE OF SAID BALANCE WHEEL, THE PLANE OF SAID INDEX WHEEL BEING PARALLEL TO THE PLANE OF SAID BALANCE WHEEL DURING ROTATION OF SAID INDEX WHEEL, (B) SAID INDEX WHEEL TILTABLE A PREDETERMINED AMOUNT IN SAID PLANE, AND A SERIES OF TEETH SPACED AROUND THE PERIPHERY OF SAID INDEX WHEEL, SAID TEETH OVERLAPPING A PORTION OF THE PERIPHERY OF SAID BALANCE WHEEL, (C) A PIN FIXED ADJACENT THE PERIPHERY OF SAID BALANCE WHEEL WITH THE LONGITUDINAL AXIS THEREOF PERPENDICULAR TO SAID PLANE, SAID PIN BEING SMALL ENOUGH TO ENTER THE SPACE BETWEEN ADJACENT INDEX WHEEL TEETH, SAID PIN HAVING A PERPENDICULAR SURFACE WHICH ENGAGES A TOOTH OF SAID INDEX WHEEL UPON MOVEMENT OF SAID BALANCE WHEEL IN ONE DIRECTION, AND SAID PIN HAVING AN INCLINED SURFACE TILTING SAID TOOTH AND SAID INDEX WHEEL SAID PREDETERMINED AMOUNT WHICH IS SUFFICIENT TO ALLOW SAID PIN TO PASS UNDER SAID TOOTH AND INTO THE SPACE BETWEEN SAID TOOTH AND AN ADJACENT INDEX WHEEL TOOTH, (D) AN ELECTRO-MAGNET HAVING ALINED OPPOSED POLES, SAID BALANCE WHEEL BEING CENTRALLY DISPOSED BETWEEN SAID POLES, AND AN ARMATURE CONNECTED TO SAID BALANCE WHEEL WITH ITS LONGITUDINAL AXIS INTERCEPTING THE AXIS OF ROTATION OF SAID WHEEL, (E) MEANS TO PERIODICALLY ENERGIZE SAID ELECTRO-MAGNET, SAID MEANS TO ENERGIZE INCLUDING SAID PIN AND SAID INDEX WHEEL, SAID PIN AND INDEX WHEEL PERIODICALLY MAKING AND BREAKING A CIRCUIT BETWEEN SAID ELECTRO-MAGNET AND A POWER SUPPLY WHEREBY THE WIPING ACTION CAUSED BY THE RELATIVE MOVEMENT BETWEEN SAID PIN AND SAID INDEX WHEEL FREES SAID CONTACTS OF CORROSION. 